This relates generally to memory modules.
A memory module typically includes a plurality of integrated circuit memories. Memory modules typically include either non-volatile memory integrated circuits or dynamic random access memory (DRAM) integrated circuits. In DRAM memory integrated circuits in memory modules, single or multiple errors are isolated to one single integrated circuit in the module. In non-volatile memory modules, such as phase change memory modules, errors may not be isolated to a single device. Multiple integrated circuits in the module can contain errors.
Thus, an error correction scheme in non-volatile memories needs to not only correct for multiple errors across multiple devices in the module but also to protect against any one of the devices failing completely. Memory integrated circuits may be built for 16-byte wide accesses. Given that cache line accesses require 64 bytes of data, a reliability scheme in a memory module with four memory integrated circuits plus one exclusive OR device requires two accesses. The first access is 16-byte wide access for data. The second access is one 16-byte wide access to access error correction bytes. The exclusive OR device protects against complete failure of a device.